The United States is opposed to Turkey and India acquiring the Russian S-400 long-range air defense systems as it requires sensitive data from the sensors of the aircraft to be fed into it in order to identify them as friend or a foe.

The details of the friendly aircraft required include information on the radar, Link-16, a special transponder called Identification of Friend or Foe (IFF) and more. It cannot operate in a stand-alone manner and will need to identify NATO-integrated Turkish aircraft and US-origin Indian Air Force planes such as C-130 and P8-I as ‘friend’.

"The S-400 can therefore shoot down any aircraft, UAV or incoming missile hundreds of kilometres away by detecting it on radar or based on the sensors being used by the flying object," said Captain (Ret’d) Vikram Mahajan, Director for Aersospace and Defense, India, at the US Indian Strategic Partnership Forum.

In a paper titled titled "Understanding why the US doesn’t want India to buy the S400," he said Turkey, a NATO member state and India, which is America's "major defence partner," have signed Communications Compatibility and Security Agreement (COMCASA) with the US. This enables them to procure specialised equipment for encrypted communications for US origin military platforms like the C-17, C-130 and P-8Is; and likely for future platforms like the 24 MH-70 Romeo anti-submarine helicopters, the Sea Guardian drones, etc.

"The threat of the compromise of data is large. The concern extends to the possibility of installation of malware on the S-400 for continued access of information," Mahajan wrote.

In addition, the US is in the process of activating the Selective Availability Anti-Spoofing Module(SAASM) in the Global Positioning Systems(GPS) in aircraft supplied to India. SAASM ensures reception of a specially encrypted GPS signal code.

India and the US also set up Link-16, which provides secure, tactical data link between the navies of the two countries. The Link-16 is also expected to be provided to ground troops to share their tactical data in future.

Moreover, the S-400 contract does not include any offset agreement. Hence, India should depend on Russia for high-level maintenance and upgrade of the S-400 system until the time it is in use.

"This purchase could result in Russia’s access to tactical data of various sensors, Link-16, and IFF of all Indian aircraft and UAVs, including those supplied by US to India, through the S-400. This is a risk that is not acceptable to the US," the expert stated.

Turkey on the other hand, is one of the few countries chosen by the US to be part of its Joint Strike Fighter Project, to manufacture the F-35 Lightning II fifth generation fighter. According to recent reports, Ankara helps manufacture 6-7 percent components for the F-35 aircraft, including components of the landing gear, fuselage, cockpit displays and aircraft engines.

The US NATO-ally has placed a $2.5 billion order for S-400 systems, other than signing a contract for 100 Lockheed Martin F-35 jets. The Pentagon sees the combination of S-400 batteries and F-35 fighters as one that may give Russia a chance to closely study the stealth jet, and tailor their air defenses to defeat it.

"The US has thus suspended the delivery of the F-35 fighters to Turkey, which was scheduled to commence last year," Mahajan said. He added that the denial is primarily to avoid a compromise of data as described above, including the very sensitive data of the stealth characteristics of the F-35 fighter.

With the threat to its proprietary technology the US is taking action to sway its allies to purchase alternatives to the Russian missile systems- Lockheed Martin's Terminal High Altitude Area Defense (THAAD) and Raytheon's Patriot missile system.

Editor comment: The views in this article are entirely that of Captain (Ret’d) Vikram Mahajan- Director for Aerospace and Defense, India at the US-India Strategic Partnership Forum.